Separation method of vinylidene fluoride and acetylene

Abstract

A method for separating VdF and acetylene, the method comprising: a step for mixing a first mixture containing VdF and acetylene with an extraction solvent, which is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2, 3, 3-trifluoro-1-propene, to obtain a mixture for extraction; and a step in which the mixture for extraction is distilled to obtain a distillate having VdF as the main component and a bottom product having an extraction solvent as the main component and further containing acetylene, respectively.

Description

Technical Field

[0001] This disclosure relates to a method for separating vinylidene fluoride and acetylene. Background Technology

[0002] Vinylidene fluoride is useful as a monomer for fluoropolymers.

[0003] For example, Patent Document 1 describes a method for separating VdF and trifluoroethane, characterized by comprising: a step of adding a first extraction solvent to a first mixture containing vinylidene fluoride (VdF) and trifluoroethane to obtain a second mixture, wherein the first extraction solvent is at least one selected from the group consisting of alcohols, ketones, esters, amides, ethers, sulfoxides and nitriles having 1 to 3 carbon atoms; and an extractive distillation step of distilling the second mixture to obtain a distillate with VdF as the main component and a bottom product containing trifluoroethane as the main component.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2015 / 072305 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The separation method described in Patent Document 1 is a method for separating VdF and trifluoroethane, but it may not be applicable to the separation of VdF and acetylene.

[0009] One objective of this disclosure is to provide a method for efficiently separating VdF and acetylene from a mixture of VdF and acetylene.

[0010] Solution for solving the problem

[0011] This disclosure includes the following methods.

[0012] <1>

[0013] A method for separating vinylidene fluoride and acetylene, comprising:

[0014] The step of mixing a first mixture comprising vinylidene fluoride and acetylene with an extraction solvent to obtain an extraction mixture, wherein the extraction solvent is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene; and

[0015] The process of distilling an extraction mixture to obtain a distillate and a bottom product, wherein the main component of the distillate is vinylidene fluoride and the main component of the bottom product is the extraction solvent, and also contains acetylene.

[0016] <2>

[0017] According to the method for separating vinylidene fluoride and acetylene described in <1>, the ratio of the molar amount of the extraction solvent to the molar amount of acetylene in the extraction mixture is 0.1 to 1000.

[0018] <3>

[0019] The method for separating vinylidene fluoride and acetylene according to <1> or <2> further includes a step of distilling the bottom product of the tower to recover the extraction solvent.

[0020] <4>

[0021] According to the separation method for vinylidene fluoride and acetylene described in <3>, the recovered extraction solvent is reused in the process of obtaining the extraction mixture.

[0022] <5>

[0023] The method for separating vinylidene fluoride and acetylene according to any one of <1> to <4>, wherein the first mixture further comprises ethylene.

[0024] <6>

[0025] The method for separating vinylidene fluoride and acetylene according to any one of <1> to <5>, wherein the extraction solvent is chloroform.

[0026] The effects of the invention

[0027] According to one aspect of this disclosure, a method for efficiently separating VdF and acetylene from a mixture is provided. Detailed Implementation

[0028] In this disclosure, the numerical range represented by "~" refers to the range in which the values ​​recorded before and after "~" are respectively the minimum and maximum values.

[0029] In the numerical ranges described in stages in this invention, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, in the numerical ranges described in this invention, the upper or lower limit value recorded in a certain numerical range can be replaced with the values ​​shown in the embodiments.

[0030] In this invention, a combination of two or more preferred methods is a more preferred method.

[0031] In this invention, when there are multiple substances equivalent to each component, unless otherwise specified, the amount of each component refers to the total amount of the multiple substances.

[0032] In this disclosure, "distillate" refers to the substance distilled from the top side of a distillation column, and "bottom product" refers to the substance distilled from the bottom side of a distillation column.

[0033] In this disclosure, "main component" refers to a component other than the main component whose molar amount is relatively small. The amount of the "main component" is preferably 50 mol% or more of the total, more preferably 60 mol% or more, further preferably 70 mol% or more, and most preferably 80 mol% or more.

[0034] In this invention, unless otherwise stated, the boiling point of the compound is a value under normal pressure, which is 1.013 × 10⁻⁶. 5 Pa.

[0035] [Separation Method]

[0036] The method for separating VdF and acetylene disclosed herein includes: a step of mixing a first mixture containing VdF and acetylene with an extraction solvent to obtain an extraction mixture, wherein the extraction solvent is at least one compound selected from the group consisting of methanol, acetone, chloroform and 1-chloro-2,3,3-trifluoro-1-propene; and a step of distilling the extraction mixture to obtain a distillate whose main component is vinylidene fluoride and a bottom product whose main component is the extraction solvent and also contains acetylene.

[0037] According to the method for separating VdF and acetylene disclosed herein, VdF and acetylene can be separated efficiently.

[0038] VdF is useful as a monomer for fluoropolymers, but if a polymerization reaction is carried out using, for example, a composition containing VdF and acetylene as an impurity, the acetylene reacts with the polymerization initiator, making the target polymerization reaction difficult to proceed. This can easily lead to a decrease in the polymerization rate or even cessation of the polymerization reaction, preventing the acquisition of the target polymer. Therefore, it is ideal to separate VdF from acetylene to obtain high-purity VdF. However, VdF has a boiling point of -83°C, while acetylene has a boiling point of -84°C. The boiling points of VdF and acetylene are close, making it difficult to separate and purify them using conventional distillation.

[0039] Patent document 1 describes a method for separating VdF and trifluoroethane, but the suitable extraction solvent in the method for separating VdF and trifluoroethane may not be the same as the suitable extraction solvent in the method for separating VdF and acetylene.

[0040] The inventors have discovered that VdF and acetylene can be efficiently separated by using an extraction solvent comprising at least one selected from the group consisting of methanol, acetone, chloroform and 1-chloro-2,3,3-trifluoro-1-propene.

[0041] The following describes each step of the method for separating VdF and acetylene disclosed herein.

[0042] <Mixed Processes>

[0043] The method for separating VdF and acetylene disclosed herein includes a step of mixing a mixture containing VdF and acetylene with a compound having a boiling point of -60°C to 0°C to obtain an extractable mixture (hereinafter also referred to as the "mixing step").

[0044] (First mixture containing VdF and acetylene)

[0045] The first mixture comprising VdF and acetylene may contain other components besides VdF and acetylene; from the viewpoint of efficiently obtaining high-purity VdF, it is preferable that the content of other components is low. Examples of other components include fluoroolefins and ethylene other than VdF. Preferably, the first mixture contains ethylene, which can be incorporated into the VdF manufacturing process.

[0046] The total content of VdF and acetylene relative to the total amount of the first mixture is, for example, 50 mol% or more, 80 mol% or more, 90 mol% or more, 99 mol% or more, or 100 mol%.

[0047] In the first mixture, the molar ratio of VdF to acetylene is not particularly limited. From the viewpoint of production efficiency, the molar ratio of acetylene to VdF (i.e., the molar ratio) is preferably 0.01 to 1, more preferably 0.01 to 0.5, and even more preferably 0.01 to 0.1.

[0048] As a first mixture, for example, a reaction product containing VdF obtained by reacting various raw materials for the purpose of producing VdF can be used.

[0049] (Extraction solvent)

[0050] The extraction solvent is at least one compound selected from the group consisting of methanol, acetone, chloroform and 1-chloro-2,3,3-trifluoro-1-propene.

[0051] Among these methods, chloroform is the preferred extraction solvent due to its excellent separation properties from acetylene. Furthermore, chloroform also provides excellent separation properties from ethylene. Ethylene has a boiling point of -103.7°C, lower than that of VdF. Therefore, conventional distillation would result in ethylene and VdF being intermingled, making separation difficult. However, by using chloroform, which has a high affinity for ethylene, VdF and ethylene can be separated.

[0052] From the viewpoint of efficiently separating VdF and acetylene in the extraction mixture, the ratio of the molar amount of extraction solvent to the molar amount of acetylene (extraction solvent / acetylene) is preferably 0.1 to 1000.

[0053] For example, as described below, when a first mixture comprising VdF and acetylene is supplied to an extractive distillation column, and an extraction solvent is subsequently supplied to the extractive distillation column, "extraction solvent / acetylene" represents the molar ratio of the amount of extraction solvent supplied to the extractive distillation column to the amount of acetylene supplied to the extractive distillation column.

[0054] In the mixing process, from the viewpoint of efficiently separating VdF and acetylene, it is preferable to select the type of extraction solvent and adjust the amount of extraction solvent added in such a way that the specific volatility Rv in the extraction mixture is greater than 1.1. The specific volatility Rv is preferably 1.2 or higher, and more preferably 1.3 or higher.

[0055] The specific volatility Rv of VdF relative to acetylene is expressed by the following formula.

[0056] Rv = (molar fraction of VdF in the gas phase / molar fraction of VdF in the liquid phase) / (molar fraction of acetylene in the gas phase / molar fraction of acetylene in the liquid phase)

[0057] There is no particular limitation on the method of mixing the first mixture containing VdF and acetylene with the extraction solvent. The extraction solvent may be added to the first mixture containing VdF and acetylene, or the first mixture containing VdF and acetylene may be added to the extraction solvent.

[0058] Furthermore, there is no particular limitation on the timing of obtaining the extraction mixture as long as it is before the extraction mixture is distilled.

[0059] From the viewpoint of efficiency of distillation of the extraction mixture (described later), it is preferable to supply an extraction solvent to an extraction distillation column containing a first mixture of VdF and acetylene, wherein the extraction mixture is prepared in the extraction distillation column and distillation is performed simultaneously with the completion of the preparation.

[0060] The extraction mixture may contain components other than VdF, acetylene, and the extraction solvent. Examples of components other than VdF, acetylene, and the extraction solvent that may be included in the extraction mixture include those found in the first mixture containing VdF and acetylene described above.

[0061] <Extraction and Distillation Process>

[0062] The method for separating VdF and acetylene disclosed herein includes a step of distilling an extraction mixture to obtain a distillate whose main component is VdF and a bottom product whose main component is the extraction solvent and which also contains acetylene (hereinafter also referred to as the "extraction distillation step").

[0063] The extractive distillation process can be carried out using commonly used distillation apparatus, such as plate columns or packed columns. Various conditions for the extractive distillation process, such as operating temperature, operating pressure, reflux ratio, total number of plates in the distillation column, position of the feed plate, and position of the extraction solvent supply plate, are not particularly limited and can be appropriately selected to achieve the desired separation. When using a plate column in the extractive distillation process, the number of plates can be, for example, 1 to 100, but from the viewpoint of obtaining high-purity VdF, 30 or more is preferred, and more preferably 50 or more. Since both VdF and acetylene have low boiling points, it is preferable to carry out the extractive distillation under pressure, for example, preferably 0 to 5 MPaG (gauge pressure).

[0064] Furthermore, the temperatures at the top and bottom of the distillation column are determined based on the operating pressure and the composition of the distillate and bottom product. Considering the temperatures of the condensers and reheaters located at the top and bottom of the column, for economical distillation operations, a top temperature of -60 to 100°C and a bottom temperature of -10 to 300°C are preferred. Extractive distillation can be batch or continuous, and depending on the circumstances, it can also be carried out in a semi-continuous manner with intermittent extraction of the distillate and bottom product, or intermittent addition. For the extraction solvent, a continuous supply to the distillation unit is preferred.

[0065] The extraction solvent described above has an affinity for acetylene. Therefore, by extractive distillation of an extraction mixture containing VdF, acetylene, and the extraction solvent, a distillate with VdF as the main component can be obtained from the top of the extractive distillation column. The composition of this distillate is not limited as long as it contains VdF as the main component, and the molar fraction of VdF in the distillate is preferably 90 mol% or more, more preferably 99 mol% or more. Furthermore, the molar fraction of acetylene in the distillate is preferably 1 / 10 or less of the molar fraction of acetylene in the extraction mixture, more preferably 1 / 100 or less. The molar fraction of acetylene in the distillate is preferably 10 mol% or less, more preferably 1 mol% or less, and even more preferably 0.1 mol% or less.

[0066] The bottom product obtained from the bottom of the extractive distillation column is an extraction solvent as the main component and also contains acetylene. The composition of this bottom product is not limited as long as it contains the extraction solvent as the main component, but the molar fraction of the extraction solvent in the bottom product is preferably 30 mol% or more, more preferably 50 mol% or more. The molar fraction of acetylene in the bottom product is preferably higher than the molar fraction of acetylene in the extraction mixture. Specifically, the molar fraction of acetylene in the bottom product is more preferably 1.1 or more of the molar fraction of acetylene in the extraction mixture, and even more preferably 2 or more.

[0067] <Distillation Process>

[0068] The method for separating VdF and acetylene disclosed herein preferably further includes a step of distilling the bottom product to recover the extraction solvent (hereinafter also referred to as the "distillation step").

[0069] The distillation process can be carried out using the same distillation apparatus as the extraction distillation process described above. Various conditions of the distillation process, such as operating temperature, operating pressure, reflux ratio, total number of trays in the distillation column, and the location of the feed trays, are not particularly limited and can be appropriately selected to achieve the desired separation.

[0070] The extraction solvent can be recovered by separating it from VdF and acetylene through a distillation process.

[0071] In the distillation process, a bottom product containing the extraction solvent is obtained from the bottom side of the distillation column. Preferably, the recovered extraction solvent is reused in the aforementioned extractive distillation process. In the VdF and acetylene separation method of this disclosure, the boiling point difference between acetylene and the extraction solvent is large, resulting in excellent separation of acetylene and the extraction solvent. Therefore, high-purity extraction solvent can be recovered, making it suitable for reuse.

[0072] Example

[0073] The embodiments of this disclosure are described in detail below, but the embodiments of this disclosure are not limited thereto. Examples 1 to 4 are embodiments, and Examples 5 to 9 are comparative examples.

[0074] <Example 1~Example 9>

[0075] Mix the following ingredients to prepare the first mixture.

[0076] • VdF: 0.134 moles

[0077] Acetylene: 0.111 moles

[0078] Ethylene: 1,000 moles

[0079] Methane: 0.0837 moles

[0080] Chloromethane: 0.0873 moles

[0081] 20 g of the compound listed in Table 1 was used as the extraction solvent. No extraction solvent was used in Example 5.

[0082] The details of “AS-300”, “AC-2000”, and “AE-3000” in Table 1 are as follows.

[0083] AS-300: Product name "AS-300", manufactured by AGC. It is a mixture of 1-chloro-2,3,3-trifluoro-1-propene (E) and 1-chloro-2,3,3-trifluoro-1-propene (Z).

[0084] AC-2000: Product name "ASAHIKLIN AC-2000", manufactured by AGC. 1,1,1,2,2,3,3,4,4,5,5,6,6-Tetrafluorohexane.

[0085] AE-3000: Product name "ASAHIKLIN AE-3000", manufactured by AGC. 1,1,2,2-Tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0086] The molar amounts of the extraction solvents listed in Table 1 are as follows.

[0087] Methanol: 0.625 moles

[0088] Acetone: 0.345 mol

[0089] Chloroform: 0.168 mol

[0090] AS300: 0.135 mol

[0091] • Carbon tetrachloride: 0.130 moles

[0092] AC2000: 0.0625 moles

[0093] ·AE3000: 0.100 moles

[0094] Cyclohexane: 0.238 mol

[0095] [Analysis Conditions]

[0096] In the determination of specific volatility, the composition of the resulting liquid was analyzed using gas chromatography (GC). A DB-1 column (60 m in length × 250 μm in inner diameter × 1 μm in thickness, manufactured by Agilent Technologies) was used.

[0097] [Determination of specific volatility]

[0098] The prepared first mixture and the required extraction solvent were injected into a pressure vessel equipped with a pressure gauge. The temperature was adjusted to a pressure of approximately 1.0 MPaG and maintained for 1 day to allow the composition within the pressure vessel to stabilize.

[0099] Then, samples from the liquid and gas phases were collected and analyzed by gas chromatography. Using the analytical results, the specific volatility of acetylene relative to VdF and the specific volatility of ethylene relative to VdF were calculated using the above formula for specific volatility. The calculated results are shown in Table 1.

[0100] [Table 1]

[0101]

[0102] As shown in Table 1, it can be seen that in Examples 1 to 4, because methanol, acetone, chloroform, or 1-chloro-2,3,3-trifluoro-1-propene was used as the extraction solvent, the specific volatility of acetylene relative to VdF was higher compared to Example 5, which did not use an extraction solvent. Specifically, in Examples 1 to 4, the specific volatility of acetylene relative to VdF was 1.1 or higher. Therefore, if these extraction solvents are used for extractive distillation, the distillate from the distillation column can yield a VdF purified product with a higher VdF content than the extraction mixture, i.e., a higher concentration of VdF, allowing for efficient separation.

[0103] In particular, in Example 3, chloroform was used as the extraction solvent. The specific volatility of acetylene relative to VdF and the specific volatility of ethylene relative to VdF were both very high, indicating that VdF and acetylene could be separated more efficiently.

[0104] On the other hand, in Examples 6 to 9, carbon tetrachloride, AC2000, AE3000 or cyclohexane were used as extraction solvents. It can be seen that the specific volatility of acetylene relative to VdF is very low, which is not suitable for the separation of VdF and acetylene.

[0105] In the method for separating VdF and trifluoroethane described in Patent Document 1, AC2000 and AE3000 are suitable as extraction solvents. However, in the method for separating vinylidene fluoride and acetylene disclosed in this paper, it is known that AC2000 and AE3000 are not suitable as extraction solvents.

[0106] It should be noted that the publication of Japanese Patent Application No. 2023-095061, filed on June 8, 2023, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described in this specification, and the specific documents, patent applications, and technical standards described separately, are incorporated herein by reference to the same extent.

Claims

1. A method for separating vinylidene fluoride and acetylene, comprising: The step of mixing a first mixture comprising vinylidene fluoride and acetylene with an extraction solvent to obtain an extraction mixture, wherein the extraction solvent is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene; and, The process of distilling the extraction mixture to obtain a distillate and a bottom product, wherein the main component of the distillate is vinylidene fluoride and the main component of the bottom product is the extraction solvent, and also contains acetylene.

2. The method for separating vinylidene fluoride and acetylene according to claim 1, wherein, In the extraction mixture, the ratio of the molar amount of the extraction solvent to the molar amount of acetylene is 0.1 to 1000.

3. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, wherein, It also includes a step of distilling the bottom product of the column to recover the extraction solvent.

4. The method for separating vinylidene fluoride and acetylene according to claim 3, wherein, The recovered extraction solvent is reused in the process of obtaining the extraction mixture.

5. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, wherein, The first mixture also contains ethylene.

6. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, wherein, The extraction solvent is chloroform.

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